The invention described herein may be manufactured, used and licensed by or for the U.S. Government.
The present invention relates generally to incendiary devices, and more particularly, to incendiary devices for producing controlled-diameter holes in metallic targets.
In the disposal of unserviceable explosive ordnances, incendiary devices are often used to burn through the ordnance casing and to ignite or otherwise destroy the ordnance payload. Thermite devices are often used for this purpose. Thermite devices are also used for unconventional warfare activities. Examples include the destruction of machinery or metallic structures, or the destruction of biological agents or precursors.
Destruction of metallic targets can be accomplished by cutting a hole through the casing steel and fusing the gears, pistons, and shaft with a stream of molten iron at 4500xc2x0 F. It has unlimited uses for attacking and destroying transformers, generators, electric motors, engine blocks, gun barrels, breech blocks, and mines. Storage tanks or drums can be cut through, causing the contents to flow out. If the liquid is flammable a fire and deflagration will result.
Destruction of biological agent and/or its precursor can be accomplished with a minimum collateral release by melting through a steel target (such as fermentation equipment, production equipment, storage drum, or warhead) to render the target unusable to an enemy and destroying the fill material by heating and incendiary action.
Thermite, one of the most common pyrotechnic incendiary agents, is essentially a mixture of powdered ferric oxide and powdered or granular aluminum. When raised to its ignition temperature, an intense reaction occurs whereby the oxygen in the ferric oxide is transferred to the aluminum, producing molten iron, aluminum oxide, and releasing approximately 750 kilocalories per gram. The reaction proceeds as follows:
8Al+3Fe3O4xe2x86x924Al2O3+9Fe
This exothermic reaction may produce a temperature of about 4500xc2x0 F. under favorable conditions. The white-hot molten iron and slag can itself prolong and extend the heating and incendiary action.
Other types of thermites containing the oxides of other metals in place of iron oxide are known: manganese thermite (4Al+3MnO2), chromium thermite (2Al+Cr2O3), and others. Iron thermite (8Al+3Fe3O4) has proved to be the most effective in incendiary composition for destruction of steel targets because superheated liquid products are formed by the reaction. These molten products affect a high rate of conductive heat transfer to the steel target and, therefore, cause destruction of the target.
However, because of the great difficulty in igniting thermite and the almost complete absence of gaseous reaction products, which causes flameless burning and a small radius of action of the hot thermite, iron-thermite is typically not used alone as an incendiary mixture. It is used in multi-component thermite-incendiary compositions, in which another oxidizer and binder are included, together with thermite. Thermate-TH3, a mixture of thermite and pyrotechnic additives, was found to be superior to thermites and was adapted for use in incendiary hand grenades. Its composition by weight is generally thermite 68.7%, barium nitrate 29.0%, sulfur 2.0% and binder 0.3%. Addition of barium nitrate to thermite increases its thermal effect, creates flame in burning and reduces the ignition temperature.
Previous efforts involving the use of pyrotechnic thermite grenades involved either the welding of two bars or of creating a pile of molten iron slag. Crude and inexpensive pyrotechnic thermite compositions were used to weld railroad rails together without the need for gas torches.
The military application of this technology resulted in the development of the AN-M14 Thermite Grenade circa 1940. It contains approximately 680 g of thermate-TH3 which releases approximately 795 kilocalories per gram of uncontrolled energy through the thin walls of its sheet metal body. This energy however, being undirected, is highly inefficient and insufficient to produce reasonable penetration levels. This M14 grenade would penetrate a xe2x85x9xe2x80x3 of mild steel and was used to disable military equipment by placing a large puddle of molten iron slag within a critical part of the item to be disabled.
Current DOD Explosive Ordinance Disposal (EOD) training school identifies the use of the standard AN-M14 incendiary grenade to render disposal of certain explosive ordinances. Unfortunately, the current EOD procedure requires several grenades, as many as 10 grenades, to achieve the desired result and the effect of the grenades in certain applications offers inconsistent effectiveness. Its configuration does not allow sufficient penetration.
A device with greater penetration capabilities is the xe2x80x9cThermite Destructive Device,xe2x80x9d U.S. Pat. No. 5,698,812 issued Dec. 16, 1997 to Eugene Song. This device was designed to create a forceful jet of molten iron through an opening at the bottom of the containing vessel. One grenade containing approximately 350 g of thermate-TH3 charge is capable of burning through a sheet of 1-inch thick steel plate in about 8 second reaction time. The device utilizes a central core-burning configuration to direct the molten products through an orifice at the bottom of the device.
While this design has merit from a penetration standpoint, and a 350 g charge of thermite could penetrate 1-inch thick steel plate, it is still inadequate to produce reasonable hole size levels. It is only capable of burning a xe2x85x9exe2x80x3 diameter hole, which is not sufficient enough for the safe disposal of an unexploded munition. A larger sized hole is needed to prevent a buildup of the internal pressure, and to achieve the successful burnout of the filler explosive. Earlier work has indicated that burning a 3xe2x80x3 diameter hole through the outer casing will allow the explosive contained in the bomb to burn without transitioning to a detonation.
For the reasons stated above, and for other reasons stated below that will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternative incendiary devices that are adapted for burning controlled-diameter holes through metallic targets.
The various embodiments provide an incendiary device utilizing a multiple core-burner technique that facilitates producing large diameter cuts through steel targets. To facilitate this result, the various embodiments incorporate a multiple-core burning design with multiple orifices at the base for directing multiple jets of molten reaction product at the target. The various embodiments further incorporate an optional holding device as a means for locking the device onto a target. Devices in accordance with the invention having a base diameter of 2.312xe2x80x3 have been shown to be capable of producing an approximately 2xe2x80x3 diameter hole through xc2xc inch thick steel plate using a 275 g thermite charge within a container three-quarters the size of a standard AN-M14 Thermite Grenade package.
For one embodiment, the invention provides an incendiary device. The device includes an insulated housing, a vented plug at a top of the housing and a nozzle plate at a bottom of the housing. The nozzle plate includes a plurality of orifices. The device further includes a thermite charge contained in the housing between the vented plug and the nozzle plate. The thermite charge includes a plurality of cores extending a length of the thermite charge between the vented plug and the nozzle plate. Each core is aligned with an orifice of the nozzle plate.
For another embodiment, the invention provides an incendiary device. The device includes a housing having a top and a bottom, a vented plug at the top of the housing, a lid at the top of the housing covering the vented plug, and a nozzle plate at the bottom of the housing. The vented plug includes an adapter for a remote initiation fuse assembly and at least one vent. The lid has a hole corresponding to each vent of the vented plug. The nozzle plate includes a plurality of orifices. The device further includes a compacted thermite charge between the nozzle plate and the vented plug, the thermite charge having a plurality of hollow cores corresponding to the plurality of orifices of the nozzle plate, and a starter material on top of the thermite charge interposed between the vented plug and the thermite charge. An air space is interposed between the starter material and the vented plug. The device still further includes an insulation liner extending from the vented plug to the nozzle plate and interposed between the thermite charge and the housing and a standoff extending below the nozzle plate. The standoff comprises a lip along the circumference or outer edge of the housing only, so that the nozzle plate is spaced apart from the target surface being penetrated. The device still, further includes impermeable seals covering each vent of the vented plug and each orifice of the nozzle plate.
For yet another embodiment, the invention provides an incendiary device having a thermite charge for burning a hole in a target surface. The incendiary device includes means for igniting the thermite charge, thereby producing molten reaction products, and means for producing a plurality of jets of the molten reaction products in an arrangement approximating a shape of a desired burn in the target surface.
The invention further includes other apparatus of varying scope.